Published on February 18, 2014
Digital Re-print January | February 2014 Design of an efficient intake pit dedusting system the state-of-the-art in technology Grain & Feed Milling Technology is published six times a year by Perendale Publishers Ltd of the United Kingdom. All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2014 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1466-3872 www.gfmt.co.uk
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F &Feed millinG technoloGy 16 | January - February 2014 Grain Design of an efficient intake pit dedusting system the state-of-the-art in technology by Andreas Rembeck and Rico Hindemith, Bühler GmbH T he unloading of bulk materials such as cereals into intake pits is generally associated with considerable dust emissions. The reasons for the need for an efficient receiving pit dust control system can be diverse. They range from reducing dust emmissions in neighboring residential areas to improving health and safety at work for those working on site and the imperative requirement of preventing serious damage to plant and danger of fatal injury from dust explosions. Bühler Grain Logistics offers a choice between two systems, depending on application requirements: namely central or distributed receiving pit dust control. These can be further subdivided on the basis of whether extraction is above or below the grid iron. Both systems are of modular design and can therefore be customized to the specific conditions of each situation. To ensure that the required aspiration capacity of the intake pit dedusting is kept to the minimum, every component needs to be optimized. It is therefore an advantage if there are gates at the entrance area which are kept closed at all times during unloading so that undesired air draughts and dust escaping to the surrounds can be prevented at the outset. For an optimum air flow inside the reception area, the upper section of the side wall is fitted with louvers. This prevents dust getting whirled up and ensures that the dust which collects is directed towards the extractors (Figure 1). Another technical step towards minimising dust emissions can be taken by installing a dust barrier. The barrier has dust retention panels (Figure 2) and prevents dust whirling up in the hopper. Practical experience from day-to-day operations has shown that up to 75 percent of the dust which is generated is produced when the bulk material hits the floor of the hopper. The dust barrier reduces air requirements, allows smaller filters and fans and cuts the power requirements of the fans by approximately 60 percent. Filters for intake pits (decentralized) For operations such as grain collection facilities or farms where the amount of dust generated is insignificant or plays only a minor role at most, decentralized dedusting is the more appropriate solution (Figure 3). In this case two adjustable inlet openings allow the air which requires cleaning to flow into the filter panels, from which it is directed to the fan through a manifold pipe line. The filter modules are connected using elements to form a single unit and the cleaned dust falls back into the reception pit via a diagonal plate. Centralized intake pit dedusting Centralized dedusting is designed more for food processors such as grain mills and producers of pasta, where removing dust from the raw product is essential. As in decentralized dedusting, the air to be cleaned is also caught by an aspiration panel. The individual aspiration modules are screwed together, which means that a variety of intake hopper sizes can be created ranging from 4 m to a maximum of 24 m in length. The aspiration panel is connected to a dust manifold pipe line which leads to a Bühler round filter. The round filter is a central filter with a jet-pulse cleaning system. This is where the flow of raw gas which is picked up and the dust which is retained are separated. The dust is conveyed through dust discharge chutes to separate dust containers or big bags. As a result, the undesired dust no longer comes into contact with the product, thereby ensuring improved hygiene and greater safety. This system could be described as a form of initial pre-cleaning. Filter Figure 1: Schematic diagram of an intake pit TA-Luft directive requirements under the German Federal Immissions Control Act stipulate emission limits of 20 milligrams of residual dust per normal cubic meter of air. The use of antistatic filter bags is one way of ensuring compliance with these reference values. They are more effective at cleaning than filter cells and also permit higher airto cloth ratios.
17 | January - February 2014 Grain Figure 3. Filters for intake pits (decentralized) Cleaning is on a time-controlled and/or differential pressure controlled basis, which ensures optimum filter performance and saves energy. Comparison The two types of intake pit dedusting systems can be designed for both side and rear unloading. With their adjustable double gap they can be customized to local conditions and are capable of aspiring even if the intake pit is overfilled. Depending on requirements the walls can be supplied with filter modules only or with partition walls as well, enabling sizes ranging from 2x3 to 4x24 square meters. &Feed millinG technoloGy Figure 4: Type RB round filter The differences between the two filter systems are as follows: whereas the decentral dedusting system has a larger surface and therefore a lower filter load than the central dust removal system, the maximum dischargeable air rate of 55 m³ per minute and meter of pit length with a filter load of 5 m³ per minute and m² of filter surface (grain) is less than the dischargeable air rate of the central solution, which is a maximum of 65 m³ per minute and meter of pit length for the same filter load. Separate dust separation means that the central version requires more space for Bühler round filters (Figure 4) and dust containers. On the other hand the decentralized dedusting system involves additional costs in terms of compressed air for cleaning the filter bags. The purchase costs of the central receiving pit dedusting system are generally higher than for a decentralized system because the former has more components. In terms of operating costs, however, the central solution normally works out better. Both systems have their advantages. The decision as to whether preference should be given to the central or decentral option depends on the specific application. www.buhlergroup.com About Bühler Figure 2: Dust retention panels Bühler is a global technology leader which specializes in the supply of equipment, systems and services for the conversion of renewable resources derived from food and synthetic substances into top quality functional products and materials. Bühler operates in over 140 countries and has some 10,000 employees worldwide. In fiscal 2012, the Group generated sales revenue of CHF 2,409 million. F
LINKS January - February 2014 This digital Re-print is part of the January | February 2014 edition of Grain & Feed Milling Technology magazine. Content from the magazine is available to view free-of-charge, both as a full online magazine on our website, and as an archive of individual features on the docstoc website. Please click here to view our other publications on www.docstoc.com. first published in 1891 • • Having no choice is not reasonable The quest for a healthier snack Design of an efficient intake pit dedusting system Silos special: Bulk storage challenges • Contact the GFMT Team • Subscribe to GFMT NIR: • Keep running costs down the state-of-the-art in technology • Visit the GFMT website In this issue: • • • See the full issue Production control in rapeseed processing using NIR technology operating en-masse chain conveyors • Getting your dies and rolls re-worked locally to global standards INCORPORATING PORTS, DISTRIBUTION AND FORMULATION A subscription magazine for the global flour & feed milling industries - first published in 1891 To purchase a paper copy of the magazine, or to subscribe to the paper edition please contact our Circulation and Subscriptions Manager on the link adove. INFORMATION FOR ADVERTISERS - CLICK HERE Article reprints All Grain & Feed Milling Tecchnology feature articles can be re-printed as a 4 or 8 page booklets (these have been used as point of sale materials, promotional materials for shows and exhibitions etc). If you are interested in getting this article re-printed please contact the GFMT team for more information on - Tel: +44 1242 267707 - Email: email@example.com or visit www.gfmt.co.uk/reprints www.gfmt.co.uk
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